This invention relates to a leading-vehicle detection apparatus that detects the distance and direction of a leading vehicle.
Prior-art leading-vehicle detection apparatuses detect the distance and direction of a leading vehicle or other objects, using a radar, an image sensor, etc. An auto-drive system has been proposed that operates an acceleration pedal based on detected distance and direction information. An auto-brake system has been also proposed that controls brakes based on the detected information.
The prior-art leading-vehicle detection apparatuses are classified into two systems: a passive system that detects obstacles by using an image sensor, and processes a picture of the detected data; and an active system that emits electromagnetic waves or laser beams forward and detects obstacles and their distances from signals reflected from the obstacles.
The passive system must process at least 10,000 units of data obtained from the image sensor. Its intricate processing circuit increases the processing time period, resulting in slow response.
On the other hand, the active system requires no intricate processing, so it has a quick response. However, a laser beam detects static objects, like a road or a guardrail as if they were moving objects like a vehicle.
To solve the problem of the active system, another leading-vehicle detection apparatus, disclosed in the Published Unexamined Patent Application No. S61-40579, addresses that problem in the active system. This prior-art apparatus emits electromagnetic waves to the rear part of the leading vehicle, which part is coated with wave-absorbing material, and distinguishes the leading vehicle from the auxiliary facilities of a road, an opposing vehicle, etc.
However, in this prior art, the leading vehicle must have a specific characteristic, i.e., a wave-absorbing coating on its rear. The prior-art apparatus can obtain information only from the leading vehicle having the specific characteristic on its rear.